Finding Water in the Desert

In a 2005 presentation before the U.S. Senate, Ed Archuleta, general manager of the El Paso Water Utilities (EPWU), said, “To accommodate the rapid population growth that is occurring in Texas, New Mexico, Arizona, Nevada and Southern California, we need to be able to reclaim and reuse our wastewater, and we need to be able to desalinate water in a cost-effective manner. Only research will allow us to do that.”

The Kay Bailey Hutchison Desalination Plant and its supporting facilities are the result, and they are benefiting from the research. The plant, named for the state’s U.S. senator who helped secure a substantial amount of funding, was part of a multiphase, $87 million, federally funded project. It was built jointly by U.S. Army Fort Bliss and the El Paso Water Utilities on Fort Bliss property. The ribbon-cutting ceremony is set for August 2007. When it opens, it will be the world’s largest inland desalination plant facility.

City model

As the first of its kind, it will serve as a model for other inland cities worldwide that face diminishing supplies of fresh water. While coastal desalination plant facilities dispose of unusable brine in the ocean, the EPWU faced challenges in building such a plant in the desert where El Paso—a city that has an annual average rainfall of only nine inches—is located.

The land the plant is on is part of the Hueco Bolson—a flat, arid 2,500-square-mile area in Texas, New Mexico and Chihuahua, Mexico—hundreds of miles from the sea. The EPWU drilled wells to draw groundwater from underground layers of rock or other materials. EPWU then pushed that water to the plant to be treated by a reverse osmosis (RO) process, which uses a membrane to desalt water. This method is more energy-efficient and less costly than many others. The treated water will be blended with water from other wells and distributed throughout the city.

The EPWU evaluated disposal options for the brine, including evaporation ponds and deep well injection. They settled on the latter and built three injection wells in the desert, 22 miles from the plant, about a mile apart. The brine will be injected into the ground.

Contractors in the sand

Several electrical contractors worked on different parts of the project: groundwater wells, injection wells and the plant itself. They worked under separate contracts.

Kendrick Electric Corp. of El Paso provided power for the pumping stations for the 32 groundwater wells spaced 2,000 to 4,000 feet apart in an arc over a 12- to 14-mile area on Fort Bliss and El Paso International Airport property. The company also connected pumps and the controls that sequence the pumping operation of the wells and installed surveillance cameras at the stations.

Since the sites are in remote areas, a photovoltaic power system and a generator backup system were installed.

Programmable logic controllers (PLC) were also installed at each of the sites. The PLC controls the water flow not just from the wells to the plant, but also in the plant and from the plant to the surface injection facilities.

“PLC controls are tied into the radio-telemetry system at each well center, and we can control the wells and the well blending from the plant so that if we need to add more water into the system, we can or vice versa,” said Dave Walters, project manager, MWI McDade-Woodcock Inc. The Albuquerque-based company was the lead electrical contractor on the desalination plant itself.

Under a separate contract, MWI McDade-Woodcock also installed remote terminal unit (RTU) cabinets and approximately 20-foot-high antennas at the wells, so the processes could be controlled remotely. The wells can also be controlled manually, bypassing the RTU controls.

Some of the automated processes controlled by the PLC include measurement of the amount of chlorine in the water, conductivity of the water or monitoring of the field equipment and instrumentation.

“The PLC controls the RPMs, the rate of the pump motors, which have variable frequency drives associated with them,” Walters said. “Our instrumentations reports to PLC, which merges and marries with the program. If one of the instruments calls for a demand, then it will report through the PLC program. Then, we also control motor operated valves to open and close the pipeline.”

MWI and its subcontractor, Wunderlich-Malec Environmental, an engineering firm with corporate headquarters in Minnetonka, Minn., and offices in 11 states, worked as a team with CDM, a consulting, engineering, construction and operations firm headquartered in Cambridge, Mass.

“Our programmer worked side by side with Wunderlich-Malec on programming to get the facility operational in an automated mode,” said Michael Scherer, CDM project manager, whose company of architects and engineers, along with their engineering partners, did the electrical design and the computer programming for the automated operation of the desalination plant.

When MWI began the project, Chuck Roberts was the project manager. The company was involved at that point in early purchasing, getting temporary power for the site and mobilizing the design aspects of their portion of the job.

“The startup was pretty complicated since we had to start integrating all the controls and instrumentation,” Roberts said. “From an electrical contractor’s standpoint, the quality that these jobs take is unusual in the adherence to specifications. The specifications couldn’t be put in one volume. It’s about 10 volumes and that part makes for a difficult job.”

One of MWI’s initial steps was to coordinate with Wunderlich-Malec.

“They are an integral part of what we do on these plants where everything is computer controlled,” Roberts said. Wunderlich-Malec provided the control panels and instrumentation equipment for the plant.

“We basically fleshed out CDM’s design. They didn’t tell us how to wire the panel. They told us what it needed to do, and we took it from there,” said Jason Greff, project manager, Wunderlich-Malec.

In turn, MWI handled all the power, lighting raceway systems and pulling of wire, as well as terminating the wiring to each of the instruments provided by Wunderlich-Malec, and ran each back to the PLC. MWI also fed the facility with two 4,000-amp three-phase services at 480 volts provided by El Paso Electric. They also installed a 150 kW generator set for critical loads in case of power loss.

MWI used different products based on the environment.

“There are chemicals used in the system that help treat the water but are very corrosive to ferrous metallic conduit. If it was a chemical building where they store chemicals, then it took different products to help preserve the system,” Roberts said.

PVC conduit and PVC-coated galvanized rigid conduit was used for underground duct banks. In wet, damp, corrosive areas, MWI used PVC-coated galvanized rigid conduit. MWI used aluminum conduit for runs on the outside of buildings. Enclosures for the junction boxes were stainless steel.

At the end of the day

Before the plant is turned over to the City of El Paso, it has to go through a series of tests. MWI will do an operational readiness test in which it will take loops or zones of the plant and test out the electrical pumps, motors and controls. Once the loops are tested out, they will proceed to the functional demonstration test in which the membranes will be loaded in the RO units, and the plant will be run as a whole, producing product. Once that test is accepted, they will conduct the site acceptance test, which will run concurrently with the 30-day performance test. MWI will be on call during that period.

“It was a heavy, detailed, industrial project. I’ve done a lot of them. They are just fun to do because you’re learning something new with every project,” Walters said.

When it is fully functioning, the plant will be a phenomenal asset to the city of El Paso and the surrounding area. The completed facilities promise to increase El Paso’s water production by 25 percent based on current demand, ensuring sufficient water availability for growth and development for the next 50 years.

CASEY, author of “Kids Inventing! A Handbook for Young Inventors” and “Women Invent! Two Centuries of Discoveries that have Changed Our World,” can be reached at scbooks@aol.com or www.susancaseybooks.com.